As is known, at present, automatic lawn mowers are predisposed to operate within predetermined cutting areas.
Lawn mowers are utilized to keep lawns, gardens and grassy areas in general, in optimal condition, that is, to keep the grass below a certain height in a substantially homogeneous manner throughout the entire cutting area.
The cutting area is often delimited by a perimeter wire or cable, in which an electrical signal is propagated; the lawn mower, detecting this electrical signal, is capable of recognizing the boundaries of the cutting area and adjusting its own movement and/or cutting activities accordingly.
As is known, lawn mowers are equipped with an independent electrical power supply unit, which has the function of supplying electrical power to the electrical and electromechanical devices present inside the lawn mower itself, such as, for example, the motors designed to drive the wheels and the blades, the electronic circuits dedicated to detection of the presence of grass, to detection of the presence of the perimeter cable, to the processing of the data collected and to controlling the various motors, etc.
When the power supply unit, which is typically made up of a battery or a battery pack, nears exhaustion, the lawn mower goes to a recharging base, where the power supply unit can be recharged so as to permit, after a certain amount of time, continuation of the activity of the lawn mower.
To date, there are various known techniques for recharging the power supply unit on board a lawn mower.
One such technique provides for a coupling of an inductive type between a first inductive element that is part of the recharging base, and a second inductive element mounted on the lawn mower and connected to the power supply unit to be recharged.
A control unit that is part of the recharging base and associated with the first inductive element, enables the flow of a pre-established current therein, so that power can be transferred to the second inductive element and the power supply unit of the lawn mower can thus be recharged.
Typically, the current delivered to the power supply unit is constant during recharging. The value of this current may be within the range of about 100 mA to 4 A.
This makes it particularly difficult to determine the most suitable value for the intensity of the current utilized, as a current that is too low can result in unduly long recharging times, whereas a current that is too high could very seriously damage the power supply unit as recharging nears completion.
In light of the above, the aim of this invention is to make available an apparatus for cutting grass, wherein the recharging of the power supply unit mounted on the lawn mower takes place in a reasonably brief time, without running the risk of damaging the power supply unit and the lawn mower.
An ancillary aim of the invention is to supply an apparatus for cutting grass, wherein the efficiency of the transfer of power from the recharging base to the lawn mower is maximized.
A further ancillary aim is to make available an apparatus for cutting grass that is capable of operating properly even when the distance between the inductive element that is part of the recharging base and the inductive element mounted on the lawn mower is fixed at a value ranging between 0 and 3 cm.
An additional ancillary aim of the invention is to provide an apparatus for cutting grass, wherein the recharging base is capable of determining in a simple and automated manner, the presence of the lawn mower so as to begin the process of recharging the power supply unit.
These and other aims are substantially achieved by an apparatus for cutting grass according to that which is described in the attached claims.
Further characteristics and advantages will become more apparent from the detailed description of a preferred, but not exclusive, embodiment of the invention.